Infrared detection camera

ABSTRACT

An infrared detection camera for the inspection of coated substrates. A corrosion sensing instrument is handheld, portable, battery powered, compact and lightweight. The camera performs nondestructive, real time imaging of corrosion and defects beneath painted metal or plastics or composite surfaces. The device includes a user-friendly computer interface for real time imaging and image storage capability and is typically used for detecting early stage corrosion beneath painted aircraft aluminum surfaces. The handheld device has a front “open air” imaging port which is designed to be placed in soft contact against the painted surface to be inspected by the instrument. The device includes an infrared camera and infrared lighting to capture an image of the surface. The captured image is transferred to a computer and analyzed to locate imperfections below a coating on a surface.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.62/274,729, filed Jan. 4, 2016 for “INFRARED DETECTION CAMERA”,incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates generally to an infrared detection camera andmore particularly to an infrared imaging system which can detectanomalies beneath a coating.

2. Description of Related Art

This invention has uses in the area of nondestructive evaluation todiscover anomalies such as stress fractures, imperfections, orcorrosions beneath a coating. Such anomalies occur beneath the coatingand are are impossible to detect visually due to the existence of thecoating.

Prior art devices generally use broad spectrum light, outside theinfrared wavelengths. Such devices can cause heating which affects anyimage obtained due to the substrate radiating heat. Such devices usesunlight or ambient light which negatively affects the quality of theanalysis. Further, such devices are generally held a distance away fromthe surface being analyzed which allows interference from effects suchas stray light, radiation, and thermal radiation. Finally, many of theprior art devices are not safe for the human eye making them dangerousto use.

U.S. Pat. Nos. 8,242,445 and 8,822,922 teach an inspection system whichcaptures an infrared image, sound information, and/or electricalmeasurement information which may be recorded. This system is complexand requires sensors, microphones, booms and audio processing equipmentto function.

U.S. Pat. No. 8,003,941 teaches a thermal imaging system which capturesa thermal image and transfers it to a computer for analysis. This systemrequires a device capable of capturing a thermal image which is based ona dummy image stored in a computer.

U.S. Pat. No. 8,253,105 teaches a system for analyzing thermal images.Again, this system requires a device capable of capturing a thermalimage. This system relies on a system of superimposing markers on thecaptured thermal image in order to perform any analysis of the capturedthermal image.

U.S. Pat. No. 8,436,311 teaches a method for predicting a thermal orchemical effect in a painted or coated composite material. This methodrequires the generation of a calibration model for each material uponwhich predictions are to be made.

U.S. Pat. Nos. 8,368,034 and 8,502,168 teach a detection system fordetecting, inspecting and classifying substances using enhancedphotoemission spectroscopy. This system uses a synchronous detector andvisible light filter for enhanced detection along with filters, asynchronous detector, databases of chemical substances and operated inthe ultraviolet range.

U.S. Pat. No. 8,937,657 teaches a portable inspection system for 3Dsurface metrology. This device generates patterns and projects them ontothe surface to be analyzed. Then the surface is photographed and imagesare captured.

U.S. Pat. No. 9,001,326 teaches a system which generates a light signalfrom a light source operating in the light spectrum and modifying thesignal by polarizing it and then reflecting the polarized signal ontothe target to observe the subsurfaces of a target material.

It is an object of the invention to provide a system for analyzingcoated surfaces.

It is further an object to provide a system for analyzing coatedsurfaces which detects anomalies beneath a coated surface.

It is further an object to provide a system for analyzing coatedsurfaces which functions in the infrared range.

It is further an object to provide a system for analyzing coatedsurfaces which reduces or eliminates the effects of ambient light and orradiation on the analysis process.

It is further an object to provide a system for analyzing coatedsurfaces which is portable, lightweight, energy efficient.

It is further an object to provide a system for analyzing coatedsurfaces which is a standalone device.

Finally, it is an object of the present invention to accomplish theforegoing objectives in a simple and cost effective manner.

The above and further objects, details and advantages of the inventionwill become apparent from the following detailed description, when readin conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

The present invention addresses these needs by providing a device forimaging coated surfaces which includes an imaging array, a lens, awindow, an infrared illumination assembly, a power source, electronicsfor providing instructions to the imaging array, for powering theinfrared illumination assembly and for capturing images, and a housinghaving a viewing port. The imaging array is preferably an infraredcamera which has a wavelength in the range of 3.4 to 4.8 microns, aresolution of 640 by 480, a frame rate of 120 kHz. The lens ispreferably made from an infrared transmitting material, such asgermanium and silicon, has an operational wavelength of 3.7 to 4.8microns, an F number of 3.25 and a 20-degree field of view. The windowis placed inside the housing above the viewing port, is preferably madeof sapphire and has a thickness of 3 mm. The infrared illuminationassembly preferably includes at least one light emitting illuminationsource and at least one reflector. The light emitting illuminationsource preferably emits high energy infrared radiation and the reflectoris preferably paraboloid. The electronics preferably include a powerswitch, a fan, a computer, an electronics board, and a video converterboard which preferably includes software for image storage and viewing.The housing is preferably constructed from a material such as metal,plastic, composite or a combination of any of these materials and mostpreferably aluminum.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete description of the subject matter of the presentinvention and the advantages thereof, can be achieved by reference tothe following detailed description by which reference is made to theaccompanying drawings in which:

FIG. 1A is a cross-sectional view of the invention in use with a coatedsubstrate with a corrosion anomaly;

FIG. 1B is an enlarged view of the infrared illumination assembly;

FIG. 2 is a rear perspective view of the preferred embodiment of theinvention;

FIG. 3 is a perspective view of the preferred embodiment of theinvention in use;

FIG. 4 is a perspective view of the preferred embodiment of theinvention in use;

FIG. 5 is a perspective view of the preferred embodiment of theinvention in use;

FIG. 6 is a miniaturized version of the invention; and

FIG. 7 is a a miniaturized version of the invention.

ELEMENT LISTING

12 imaging system

14 power supply

16 imaging array

18 lens

20 sapphire window

22 infrared illumination

24 topcoat

26 primer

28 substrate

30 corrosion

32 emitter

34 reflector

36 computer

38 electronics

40 computer

42 housing

44 viewing port

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description is of the best presently contemplatedmode of carrying out the invention. This description is not to be takenin a limiting sense, but is made merely for the purpose of illustratinggeneral principles of embodiments of the invention. The embodiments ofthe invention and the various features and advantageous details thereofare more fully explained with reference to the non-limiting embodimentsand examples that are described and/or illustrated in the accompanyingdrawings and set forth in the following description. It should be notedthat the features illustrated in the drawings are not necessarily drawnto scale, and the features of one embodiment may be employed with theother embodiments as the skilled artisan recognizes, even if notexplicitly stated herein. Descriptions of well-known components andtechniques may be omitted to avoid obscuring the invention. The examplesused herein are intended merely to facilitate an understanding of waysin which the invention may be practiced and to further enable thoseskilled in the art to practice the invention. Accordingly, the examplesand embodiments set forth herein should not be construed as limiting thescope of the invention, which is defined by the appended claims.Moreover, it is noted that like reference numerals represent similarparts throughout the several views of the drawings.

The infrared detection camera 12 according to the present invention is acorrosion sensing instrument which is preferably handheld, portable,battery powered, compact and lightweight. The camera performsnondestructive, real time imaging of corrosion and defects beneathpainted metal or plastics or composite surfaces. Defects such as stressfractures, imperfections and corrosion can be detected beneath acoating. The device preferably includes user-friendly computer interfacefor real time imaging and image storage capability and is typically usedfor detecting early stage corrosion beneath painted aircraft aluminumsurfaces. The camera can also be used for nondestructive imaging ofdefects and various textured features beneath painted surfaces. Thepreferably handheld device has a front “open air” imaging port which isdesigned to be placed in soft contact against the painted surface to beinspected by the instrument.

An imaging device 12 according to the present invention is shown incross-sectional view in FIGS. 1A and 1B and in perspective view in FIG.2. The device includes an imaging array 16, a lens 18, a sapphire window20, an infrared illumination assembly 22, a power source 14, electronicsfor providing instructions to the imaging array and for capturingimages, all within a housing.

The imaging array 16 preferably includes an infrared camera with awavelength of operation in the range of 3.4 to 4.8 microns, resolutionof 640×480, a frame rate of 120 kHz and dimensions of 60 mm×50 mm×50 mm.The imaging array 16 of the preferred embodiment consists of a mid-waveinfrared high performance and compact CCD camera from DRS, the ZafiroMicro 640.

The lens 18 is preferably made of an infrared transmitting material suchas silicon (Si) or germanium (Ge), has an operational wavelength of 3.7to 4.8 microns, an F number of 3.25 and a 20-degree field of view. Thelens 18 of the preferred embodiment is a custom mid-wave infrared(“MWIR”), low f-number lens selected for high light gathering power fromNovatech.

The device preferably includes a sapphire window 20 for protecting thelens 18. The window 20 is designed for infrared transmission and formedto fit above the viewing port (described below). In the preferredembodiment, the window 20 has a size of 1.5 inches×1.5 inches and athickness of 3 mm, such as is available from the Mell Griot Corp.

The infrared illumination assembly 22 preferably uses a two-dimensionalphotonic crystal structure to tune and confine the IR emission in the3-5 micron spectral range. The source provides high energy infraredradiation with minimal energy consumption. In the preferred embodiment,the infrared assembly includes electrically efficient MWIR lightemitting illumination sources 32 from Boston Electronics, the TuneIR35and modified paraboloid reflectors 34 for MWIR as the illuminationsource, from Mouser Electronics. In the preferred embodiment eight MWIRlight emitting illumination sources 32 are positioned and offset fromthe viewing port (described below) in order to uniformly illuminate theviewing port at an angle of between 30 and 60 degrees from the normalsurface of the viewing port.

The power source 14 is preferably a lithium ion battery but may be anytype of battery used for similar electronic devices, preferablyrechargeable. In the preferred embodiment, the battery 14 powers thedevice 12 for at least two hours of continuous usage. Although reducingthe portability of the device, the power source may be external to thehousing, in the form of, for example, AC power.

The electronics include a power switch, power for lights and fan. In thepreferred embodiment, the electronics include custom Lab View drivensoftware for image storage and viewing on computer, a touch-pad tabletcomputer, a custom electronics board for electrically powering thedevice's electronic elements (the camera, electronic boards, lights,fan, etc.), and a video converter board to send images from the MWIRcamera to the tablet computer.

The housing is rigid and weather resistant and is preferably metal,plastic or a composite material. In the preferred embodiment, thehousing is a custom aluminum housing for ergonomic, efficient and ruggedpackaging of the device components. Also inside the housing of thepreferred embodiment are shock mounts for vibration and shock isolationof the MWIR camera and cooling fan and heat dissipation fins forremoving heat generated by MWIR camera. In the forward portion of thepreferred embodiment of the invention is an open-air viewing portmeasuring 2″×2″, which can be scaled for different sized devices. Theviewing port is imaged by the custom lens and the MWIR camera which islocated approximately five inches back from the viewing port. Thehousing may include a heat sink to dissipate excess heat and cool thedevice.

In use, continuous real time imaging of the 2″×2″ viewing port is at avideo rate of about 30 Hz. Each image is captured by touch screenbuttons on tablet computer.

Function of the infrared camera detection device.

Aircraft paint, while opaque to visible light, is more transparent tomid wave infrared wavelengths in the 3-5 micron range. Aluminumcorrosion and/or defects or other surface texturing beneath a paintedsurface 24/26/28 usually has different reflectivity scattering than thesurrounding painted material. In operation (shown in FIGS. 3, 4 and 5),a portion of the infrared light passes through the coating (topcoat 24and primer 26) and reflects or scatters off the substrate 28 such thatthe camera device 12 captures the reflection. With a suitable MWIRcamera 16 and lighting source 22, these types of sub-painted featurescan be imaged and visually presented on a computer screen for the userto see these subsurface features without any damage coming to thepainted surface 24/26/28. The infrared camera detection device 12preferably has a viewing port of two inches by two inches which ispreferably placed on the surface 24/26/28 to be inspected. By placingthe device directly on or very close to the surface 24/26/28 to beinspected, effects from the external environment (such as radiation orthermal radiation) or ambient light is reduced or eliminated, resultingin improved images. By having the device 12 focus at the viewing port,user error is reduced because the user does not have to approximate howfar from the surface 24/26/28 the device 12 must be held, instead, theviewing port of the device 12 is simply placed on the surface 24/26/28to be inspected. For faster inspection, the viewing port can be madelarger, for example, ten inches by ten inches

The infrared camera detection device 12 has a suitable MWIR camera 16and uniform MWIR lighting source that is packaged to facilitate theimaging of the desired subsurface features. In the preferred embodiment,the packaging and viewing area are arranged to provide a rugged,handheld instrument 12 that is portable and is capable of providing realtime video and includes a selectable image capturing feature. Theinfrared camera detection device is designed to operate continuously forabout 2 hours on a single charge of the rechargeable batteries.

Other embodiments can be made to increase viewing area, improve imageprocessing and capture, or to extend battery life. The preferredembodiment provides a device 12 with optimal size, weight, efficiency,portability and cost.

By using only light in the infrared wavelengths, heating of the surface24/26/28 being inspected is prevented, resulting in an improved imageand eliminates the possibility of damaging the surface 24/26/28.Additionally, the device 12 is safe to the eye and uses only the powerneeded for the infrared wavelengths.

The preferred embodiment is described as being used for inspectingpainted aircraft surfaces but the device can also be used for theinspection of, military hardware, structural health monitoring, oil &gas pipelines, inspection of chemical storage tanks, inspectingautomobiles, ships & submarines, inspecting nuclear pipes & structuresand antenna dishes.

Of particular import, the device 12 is designed to be placed directly onor very near to the surface 26/28/30 being inspected. This is asignificant improvement over the prior art which requires cameras to beheld a set distance away from the surface being inspected. This requiresthe user to either measure the distance every time or to guess at thedistance resulting in poor images. By placing the viewing port 44directly on the surface 26/28/30 to be inspected, this eliminatesguesswork and provides consistently good images. This is accomplished byusing infrared light sources 22 which are very efficient for electric toinfrared radiation conversion; this results in very low heat generation.This compact device 12 can be placed directly on sensitive surfaces,such as paint, without causing any heat damage. Secondly, the lens 18 isdesigned so that when the device 12 is placed on the painted surface26/28/30, the camera 16 is able to capture an image in focus. Thirdly,by placing a soft material, such as rubber, at the outer edge of theviewing port 44, when the device 12 makes contact with paint, it doesnot affect the surface's structural integrity. Lastly, the entireequipment weighs about 4 pounds, so it is hand held and can easily beplaced on the paint's surface. Previously known devices are too largeand heavy to be placed directly on the surface and maneuvered around thesurface. The preferred embodiment of the invention can be moved over thepaint's surface by hand and the camera 16 will continue to captureimages in real time. These images are preferably displayed on thecomputer 36 mounted on the device 12. If desired, the weight of thedevice 12 can be further reduced by removing the computer 36 from thedevice 12 and holding it separately, for example on a wrist band. Thesignal from the corrosion sensor can be sent wirelessly or through acable.

Obviously, many modifications may be made without departing from thebasic spirit of the present invention. Accordingly, it will beappreciated by those skilled in the art that within the scope of theappended claims, the invention may be practiced other than has beenspecifically described herein. Many improvements, modifications, andadditions will be apparent to the skilled artisan without departing fromthe spirit and scope of the present invention as described herein anddefined in the following claims.

What is claimed is:
 1. An infrared camera device, said devicecomprising: an imaging array; a lens; a window; an infrared illuminationassembly; a power source; electronics for providing instructions to theimaging array, for powering the infrared illumination assembly and forcapturing images; and a housing having a viewing port.
 2. A cameradevice as in claim 1 wherein said imaging array is an infrared camera.3. A camera device as in claim 2 wherein said infrared camera has awavelength in the range of 3.4 to 4.8 microns.
 4. A camera device as inclaim 2 wherein said infrared camera has a resolution of 640 by
 480. 5.A camera device as in claim 2 wherein said infrared camera has a framerate of 120 kHz.
 6. A camera device as in claim 1 wherein said lens ismade from an infrared transmitting material.
 7. A camera device as inclaim 1 wherein said lens is made from an infrared transmitting materialselected from the group consisting of germanium and silicon.
 8. A cameradevice as in claim 1 wherein said lens has an operational wavelength of3.7 to 4.8 microns.
 9. A camera device as in claim 1 wherein said lenshas an F number of 3.25.
 10. A camera device as in claim 1 wherein saidlens has a 20 degree field of view.
 11. A camera device as in claim 1wherein said window is placed inside the housing above the viewing port.12. A camera device as in claim 1 wherein said window has a thickness of3 mm.
 13. A camera device as in claim 1 wherein said infraredillumination assembly includes at least one light emitting illuminationsource and at least one reflector.
 14. A camera device as in claim 13wherein said at least one light emitting illumination source emits highenergy infrared radiation.
 15. A camera device as in claim 13 whereinsaid at least one reflector is paraboloid.
 16. A camera device as inclaim 1 wherein said electronics include: a power switch, a fan, acomputer, an electronics board, and a video converter board.
 17. Acamera device as in claim 1 wherein said electronics include softwarefor image storage and viewing.
 18. A camera device as in claim 1 whereinsaid housing is constructed from a material selected from the groupconsisting of metal, plastic, composite and a combination of thesematerials.
 19. A camera device as in claim 1 wherein said housing isconstructed from aluminum.
 20. A camera device as in claim 1 whereinsaid window is sapphire.